1. Field of the Invention
The invention relates to a device for selectively authorising the bearer of a coded card to pass through a door in a wall.
2. Description of the Prior Art
In establishments where, for reasons of security, access to the establishment or to certain areas thereof is restricted to certain authorised persons, it is current practice to provide such persons with keys opening only the locks of those doors providing access to the areas of the establishment to which access is authorised. The number of possible combinations is relatively small, in that each lock can only accept a small number of differently patterned keys. In other words, it is the locks which define the operating key categories, so that the various areas of the establishment are of fixed configuration, unless these locks are changed. Moreover, keys may be stolen or copied, in which case continuing security calls for the replacement of all locks opened by the key which might be used to secure unauthorised entry.
It has already been proposed to substitute for these keys cards carrying a recorded digital signal, in particular a signal recorded magnetically. French Pat. No. 2 107 529 describes a device using a magnetic card and designed especially for use in hotels. A card reader adjacent the door to which the magnetic card is allocated is connected to a remotely sited central system. The signal read from the magnetic card and a card reader identifying signal are sent to the central system. Using data stored in its memory, the central system operating program decides if the card corresponds to the door in question and if the card is currently valid. If this is the case, the central system sends a command signal to means for opening or permitting opening the door, such as an electrically operated striking box. The number of possible combinations is very substantially increased, not only in that the encoded signal on the card may embody a much larger number of items of information than the pattern of a key, but also because it is the signal on the card and not the lock which is the determining factor in authorising access. While a key is associated with one or more locks, the card is associated with its bearer. The use of a remotely sited central system means, however, that the card reader must be similar to and connected to the central system in the same way as a computer peripheral. The reliability of the system is dependent on the quality of the link to the central unit.
French patent application No. 2 325 992 describes a stand-alone device operated by magnetic cards and programmed to authorise or prohibit access to one or more cards. A memory records a first list of authorising signals and a second list of prohibiting signals. The door is openable if the signal on the card inserted in the reader appears in the list of authorising signals and does not appear in the list of prohibiting signals. This arrangement is simpler than that using a central control system, and its operation is not dependent on the quality of links to a central unit or on the level of availability of the central unit. The arrangement is a relatively rigid one, however, in that when authorisation is withdrawn from a card bearer by writing the corresponding details into the prohibiting signal list it is no longer possible to revalidate the authorisation. This means that there is no facility for modifying authorisations at a later date.
Also, writing data into the prohibiting signal list involves connecting a manual programming unit to the card reader.
Prior art devices, whether operating on a stand-alone basis or in conjunction with a central unit, are designed to selectively authorise passage through a door in one direction, movement through the door in the opposite direction being unrestricted. Selective authorisation of access in both directions would require the use of a card reader on each side of the wall containing the door. Furthermore, there is no provision for checking that opening of the door is followed by its closure, so that should an authorised person happen to forget to close the door, access would be unrestricted. Finally, should an authorised person forget to retrieve his card from the reader, any other person is free to make use of the card of open the door.
The present invention is intended to provide a stand-alone device for selectively authorising passage through a door in both directions and returning the card to the user only when the door has been closed again.